Transmission unit

ABSTRACT

In a transmission, particularly a motor vehicle transmission, having a first, a second, a third, and a fourth planetary gear unit disposed along a main axis of rotation and having six clutch units providing for nine forward gears to be engaged, a drive unit is connected for rotation with a sun gear of the second planetary gear unit and a fourth planetary carrier of the fourth planetary gear transmission and further a power output unit is rotationally fixedly connected to a third planetary carrier of the third planetary gear unit.

This is a Continuation-In-Part application of pending international patent application PCT/EP2009/006956 filed Aug. 26, 2009 and claiming the priority of German patent application 10 2008 055 626.2 filed Nov. 3, 2008.

BACKGROUND OF THE INVENTION

The invention relates to a transmission unit for a power train of a motor vehicle including four planetary gear units and six clutch units. It is the principal object to of the invention provide a compact transmission unit with a high number of forward transmission gears.

SUMMARY OF THE INVENTION

In a transmission, particularly a motor vehicle transmission, having a first, a second, a third, and a fourth planetary gear unit disposed along a main axis of rotation and having six clutch units providing for nine forward gears to be engaged, a drive unit is connected for rotation with a sun gear of the second planetary gear unit and a fourth planetary carrier of the fourth planetary gear unit and further a power output unit is rotationally fixedly connected to a third planetary carrier of the third planetary gear unit.

A transmission unit of compact design can be provided thereby, which also has a large number of gears with good stepping and sufficient spread.

A “clutch unit” is particularly meant to be a clutch unit and also a brake unit. A “clutch unit” is particularly meant to be a unit which is provided to optionally connect or to separate two clutch elements arranged rotationally in a rotationally fixed manner. A “brake unit” is particularly meant to be a unit which is provided to optionaly connect or separate a rotational clutch element to a fixed unit, particularly a transmission housing, in a rotationally fixed manner.

“A first, a second, a third and a fourth planetary gear unit, which are arranged along a main axis of rotation sequentially” are meant to be in this connection particularly a sequence of four planetary gear units, which are arranged along the main axis of rotation in this sequence, wherein the first planetary gear unit is advantageously facing the drive shaft. For simplification, a “first to fourth planetary wheel carrier”, a “first to fourth sun wheel” and a “first to fourth hollow wheel” shall be meant to be a planetary wheel carrier or a sun wheel or a hollow wheel assigned to the first to fourth planetary gear unit, that is for example that the first planetary wheel carrier is meant to be a planetary wheel carrier of the first planetary gear unit.

Advantageously, at least one of the clutch units is provided to block at least one of the planetary gear units. One of the clutch units is particularly preferred provided to block the second planetary gear unit. A “blocked planetary gear unit” is meant to be a planetary gear unit where the sun wheel, the planetary wheel carrier and the hollow wheel are connected to each other in a rotationally fixed manner. A “blocking of a planetary gear unit” is particularly meant to be that at least two transmission elements of the planetary gear unit are connected to each other in a rotationally fixed manner, wherein the transmission elements are meant to be the sun wheel, the hollow wheel and the planetary wheel carrier. In order to block a planetary wheel carrier, it is basically also conceivable to connected the planetary wheel carrier to planetary wheels guided by the planetary wheel carrier in a rotationally fixed manner, whereby the transmission elements are also connected to each other in a rotationally fixed manner.

Two exemplary embodiments of the invention will be described below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

It is shown in:

FIG. 1 a schematic depiction of the transmission according to the invention,

FIG. 2 exemplary transmission ratios for forward transmission gears of the transmission of FIG. 1,

FIG. 3 a shift logic of the transmission of FIG. 1,

FIG. 4 a shiftability of the transmission of FIG. 1,

FIG. 5 an alternatively designed transmission and in

FIG. 6 a shift logic of the transmission of FIG. 5.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a transmission designed as a motor vehicle transmission. The transmission has four planetary gear units P1 a, P2 a, P3 a, P4 a. The first planetary gear unit P1 a, the second planetary gear unit P2 a, the third planetary gera unit P3 a and the fourth planetary gear unit P4 a are arranged behind one another along a main axis of rotation 10 a. All planetary gear units P1 a, P2 a, P3 a, P4 a of the transmission have a single planetary wheel set. The transmission has six clutch units S1 a, S2 a, S3 a, S4 a, S5 a, S6 a. These are provided to shift exactly nine forward transmission gears V1 a, V2 a, V3 a, V4 a, V5 a, V6 a, V7 a, V8 a, V9 a. The transmission can however also be operated with only eight forward transmission gears, for example in that the first forward transmission gear V1 a or the ninth forward transmission gear V9 a is not shifted.

The transmission is provided to connect a drive engine of a motor vehicle, not shown in detail, to drive wheels of the motor vehicle, not shown in detail. A transmission ratio between the drive engine and the drive wheels can be adjusted by means of the transmission. The transmission can be connected to a hybrid drive module, by means of which the drive torque can be changed. Furthermore, a CVT can be realized by means of the hybrid drive module and the transmission, whereby a transmission can be realized, whose transmission ratio can be adjusted in a stepless manner at least in partial regions.

The transmission has a drive unit 11 a, which is provided to introduce a drive torque into the transmission. A module, not shown in detail, can be connected upstream of the drive unit 11 a, which module shall be provided in particular to provide a start-up functionality. A transducer or a wet start-up clutch is for example conceivable as a module that is connected upstream. The module provided for the start-up can basically also be integrated into the transmission or one of the clutch units S1 a, S2 a, S3 a, S4 a, S5 a, S6 a can for example be used for the start-up.

The transmission further has a power output 12 a, which is provided to divert In a transmission, particularly a motor vehicle transmission, having a first, a second, a third, and a fourth planetary gear unit disposed along a main axis of rotation and having six clutch units providing for nine forward gears to be engaged, a drive unit is connected for rotation with a sun gear of the second planetary gear unit and a fourth planetary carrier of the fourth planetary gear transmission and further a power output unit is rotationally fixedly connected to a third planetary carrier of the third planetary gear unit.a drive torque from the transmission. The power output 12 a is provided to be connected to drive wheels of the motor vehicle. A module, not shown in detail, can be connected downstream of the power output 12 a, by means of which module the torque diverted from the transmission can be distributed to the drive wheels, as for example a differential gear transmission which is provided for a speed compensation between the drive wheels, or an all wheel drive unit, which distributes the drive torque to two different drive axles. The drive unit 11 a and the power output 12 a can basically be arranged relative to each other in an arbitrary manner. A coaxial arrangement on opposite sides of the transmission is thereby particularly advantageous. An arrangement on the same side of the transmission unit is however also conceivable.

The first planetary gear unit P1 a is arranged on the input side. The first planetary gear unit P1 a has a single planetary wheel set. The single planetary wheel set comprises a first sun wheel P11 a, a first hollow wheel P13 a and a first planetary wheel carrier P12 a. The planetary wheel carrier P12 a carries planetary wheels P14 a on a circular path. The planetary wheels P14 a cog with the sun wheel P11 a and with the hollow wheel 13 a. The planetary wheels are mounted rotatably on the planetary wheel carrier P12 a. The first planetary gear transmission P1 a has a transmission ratio of −1.970 between the sun wheel P11 a and the hollow wheel P13 a with a fixed planetary wheel carrier P12 a.

The second planetary gear unit P2 a is arranged centrally on the input side. The second planetary gear unit P2 a has a single planetary wheel set. The single planetary wheel set comprises a second sun wheel P21 a, a second hollow wheel P23 a and a second planetary wheel carrier P22 a. The planetary wheel carrier P22 a carries planetary wheels P24 a on a circular path. The planetary wheels P24 a cog with the sun wheel P21 a and with the hollow wheel P23 a. The planetary wheels are mounted rotatably on the planetary wheel carrier P22 a. The second planetary gear unit P2 a has a transmission ratio of −1.658 between the sun wheel P21 a and the hollow wheel P23 a with a fixed planetary wheel carrier P22 a.

The third planetary gear unit P3 a is arranged centrally on the output side. The third planetary gear unit P3 a has a single planetary wheel set. The single planetary wheel set comprises a third sun wheel P31 a, a third hollow wheel P33 a and a third planetary wheel carrier P32 a. The planetary wheel carrier P32 a guides planetary wheels P34 a on a circular path. The planetary wheels P34 a cog with the sun wheel P31 a and with the hollow wheel P33 a. The planetary wheels are mounted rotatably on the planetary wheel carrier P32 a. The third planetary gear unit P3 a has a transmission ratio of −2.548 between the sun wheel P31 a and the hollow wheel P33 a with a fixed planetary wheel carrier P32 a.

The fourth planetary gear unit P4 a is arranged on the output side. The fourth planetary gear unit P4 a has a single planetary wheel set. The single planetary wheel set comprises a fourth sun wheel P41 a, a fourth hollow wheel P43 a and a fourth planetary wheel carrier P42 a. The planetary wheel carrier P42 a guides planetary wheels P44 a on a circular path. The planetary wheels P44 a cog with the sun wheel P41 a and with the hollow wheel P43 a. The planetary wheels P44 a are mounted rotatably on the planetary wheel carrier P42 a. The fourth planetary gear unit P43 a has a standing transmission ratio of −2.648 between the sun wheel P41 a and the hollow wheel P43 a with a fixed planetary wheel carrier P42 a.

The three clutch units S3 a, S4 a, S6 a are formed as clutch units. They respectively have a first rotatable clutch element S31 a, S41 a, S61 a and a second rotatable clutch element S32 a, S42 a, S62 a. The three clutch units S3 a, S4 a, S6 a are respectively provided to connect their two clutch elements S31 a, S32 a, S41 a, S42 a, S61 a, S62 a in a rotationally fixed manner.

The three clutch units S1 a, S2 a, S5 a are formed as brake units and respectively only have one clutch element S11 a, S21 a, S51 a. The clutch units S1 a, S2 a, S5 a are respectively provided to connect their clutch element S11 a, S21 a, S51 a to a transmission housing in a rotationally fixed manner.

The clutch units S1 a, S2 a, S5 a in the form of brake units are provided on the outside. The clutch units S3 a, S4 a, S6 a in the form of clutch units are arranged on the inside. The clutch units S1 a, S2 a, S3 a, S4 a include disc packets. The clutch unit S5 a is designed as a dog clutch unit. It has a synchronising unit, not shown in detail, which can basically also be omitted. The clutch unit S5 a can however also be formed as a disc packet. The clutch units S1 a, S2 a are arranged in the axial direction at the input side from the first planetary gear unit P1 a. The clutch units S3 a, S4 a are arranged in the axial direction between the second planetary gear unit P2 a and the third planetary gear unit P3 a. The clutch unit S5 a is arranged in the axial direction at the height of the third planetary gear unit P3 a. The clutch unit S6 a is arranged in the axial direction at the height of the fourth planetary gear unit P4 a.

The drive unit 11 a is connected to the second sun wheel P21 a and the fourth planetary wheel carrier P42 a in a rotationally fixed manner by means of a drive shaft 14 a which is connected to the drive unit 11 a. The first sun wheel P11 a and the clutch element S21 a of the second clutch unit S2 a are connected in a rotationally fixed manner by means of a connection shaft 16 a. The first hollow wheel P13 a, the clutch element S42 a of the fourth clutch unit S4 a, the third sun wheel P31 a and the fourth sun wheel P41 a are connected in a rotationally fixed manner by means of a connection shaft 17 a. The clutch element S11 a of the first clutch unit S1 a, the second planetary wheel carrier P22 a, the clutch element S32 a of the third clutch unit S3 a and the clutch element S41 a of the fourth clutch unit S4 a are connected in a rotationally fixed manner by means of a connection shaft 18 a. The first planetary wheel carrier P12 a, the second hollow wheel P23 a and the clutch element S31 a of the third clutch unit S3 are connected in a rotationally fixed manner by means of a connection shaft 19 a. The third hollow wheel P33 a is directly connected to the clutch element S51 a of the fifth clutch unit S5 a in a rotationally fixed manner. The fourth hollow wheel P43 a is directly connected to the clutch element S61 a of the sixth clutch unit S6 a in a rotationally fixed manner. The power output unit 12 a is connected in a rotationally fixed manner to the third planetary wheel carrier P32 a and the clutch element S62 a of the sixth clutch unit S6 a by means of a power output shaft 15 a.

The drive shaft 14 a, which is connected to the drive unit 11 a, passes through the four sun wheels P11 a, P21 a, P31 a, P41 a. The second hollow wheel P23 a is directly connected to the drive shaft 14 a. For the connection of the fourth planetary wheel carrier P42 a, it is guided axially and radially between the fourth planetary gear transmission P4 a and the power output shaft 15 a. The connection shaft 16 a is guided radially to the outside on the axial input side from the first planetary gear unit P1 a. The connection shaft 17 a surrounds the second planetary gear unit P2 a. For the connection of the third sun wheel P31 a and the fourth sun wheel P41 a, it is guided radially and axially to the inside between the clutch unit S4 a and the third planetary gear unit P3 a. The connection shaft 18 a is guided on the inputside to the outside by the connection shaft 16 a. The connection shaft 18 a limits the transmission unit on the input side. It further passes through the first sun wheel P11 a and is guided to the outside radially and axially between the planetary gear units P1 a, P2 a for connecting the second planetary wheel carrier 22 a. For the connection of the clutch element S42 a, it passes through the second planetary gear unit P2 a and is guided radially and axially to the outside between the connection shafts 17 a, 19 a. The connection shaft 19 a is guided radially and axially to the outside between the first planetary gear transmission P1 a and the second planetary gear unit P2 a. At the output side of the second planetary gear unit P2 a, the connection shaft 19 a connects the clutch element S31 a to the clutch unit S3 a. The power output shaft 15 a is guided axially and radially to the outside between the third planetary gear unit P3 a and the fourth planetary gear unit P4 a. It surrounds the fourth planetary gear unit P4 a and limits the transmission unit on the output side.

Different hybrid drive modules can be combined by means of the transmission unit. A first drive machine of the hybrid drive module can be connected to the drive unit 11 a or the drive shaft 14 a for realizing a starter generator. For realizing a CVT, a further drive machine of the hybrid drive module can additionally be connected to an advantageous shaft of the transmission, as for example to the connection shaft 17 a, which is connected to the third sun wheel P31 a in a rotationally fixed manner.

The forward transmission gears V1 a-V9 a are shifted by means of the clutch units S1 a, S2 a, S3 a, S4 a, S5 a, S6 a (see FIG. 3). In the forward transmission gears V1 a-V9 a described in the following, respectively at the most three of the clutch units S1 a, S2 a, S3 a, S4 a, S5 a, S6 a are closed, while the remaining clutch units S1 a, S2 a, S3 a, S4 a, S5 a, S6 a are opened. With a shift process from one of the forward transmission gears V1 a-V9 a, at the most respectively only two of the clutch units S1 a, S2 a, S3 a, S4 a, S5 a, S6 a are changed. With every shift process from one of the forward transmission gears V1 a-V9 a into an adjacent forward transverse transmission gear V1 a-V9 a, respectively two clutch units S1 a, S2 a, S3 a, S4 a, S5 a, S6 a which are already closed remain closed.

The second hollow wheel P23 a and the second planetary wheel carrier can be connected in a rotationally fixed manner by means of the clutch unit S3 a, whereby the second planetary gear transmission P2 a can be blocked by means of the clutch unit S3 a. The first planetary wheel carrier P12 a and the second hollow wheel P23 a and the first hollow wheel P13 a and the second planetary wheel carrier P22 can be connected in a rotationally fixed manner by means of the clutch units S3 a, S4 a. As the second planetary gear transmission P2 a is blocked in this case, the first planetary gear transmission is thereby also blocked and connected in a rotationally fixed manner to the second planetary gear transmission P2 a.

The first forward transmission gear V1 a has a transmission ratio i₁a of 5.525 between the drive unit 11 a and the power output unit in this embodiment. The first forward transmission gear V1 a is formed by closing the clutch units S2 a, S4 a, S5 a. The clutch unit S2 a connects the first sun wheel P11 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S4 a connects the second planetary wheel carrier P22 a to the first hollow wheel P13 a and the third sun wheel P31 a in a rotationally fixed manner. The clutch unit S5 a connects the third hollow wheel P33 a to the transmission housing 13 a in a rotationally fixed manner.

The second sun wheel P21 a rotates with a same speed as the drive unit 11 a. The second planetary wheel carrier P22 a rotates with a same speed as the first hollow wheel P13 a. The second hollow wheel P23 a rotates with a same speed as the first hollow wheel P12 a. As the first sun wheel P11 a is fixed, a speed ratio between the first planetary wheel carrier P12 a and the first sun wheel P11 a is defined by means of the standing transmission ratio of the first planetary gear transmission P1 a, whereby a speed ratio between the second hollow wheel P23 a and the second planetary wheel carrier P22 a is also defined. A speed of the second planetary wheel carrier P22 a is thus defined by the speed of the second sun wheel P21 a and the standing transmission ratio of the first planetary gear unit P1 a. The third sun wheel P31 a has the same speed as the second planetary wheel carrier P22 a. As the third hollow wheel P33 a is fixed, a speed of the third planetary wheel carrier P32 a is defined by the speed of the third sun wheel P31 a and the standing transmission ratio of the third planetary gear unit P3 a. The power output unit 12 a has the same speed as the second planetary wheel carrier P22 a. A power flow for the first transmission gear V1 an is introduced via the second planetary gear unit P2 a and split via the clutch unit S4 a. A part of the power flow is fed back to the second planetary gear unit P2 a via the first planetary gear transmission P1 a. A further part of the power flow is diverted via the third planetary gear transmission P3 a.

The second forward transmission gear V2 a has a transmission ratio i₂a of 3.548 between the drive unit 11 a and the power output unit 12 a in this embodiment. The second forward transmission gear V2 a is formed by closing the clutch units S3 a, S4 a, S5 a. The clutch unit S3 a connects the second planetary wheel carrier P22 a to the second hollow wheel P23 a and the first planetary wheel carrier P12 a in a rotationally fixed manner. The clutch unit S4 a connects the second planetary wheel carrier P22 a to the third sun wheel P31 a in a rotationally fixed manner. The clutch unit S5 a connects the third hollow wheel P33 a to the transmission housing 13 a in a rotationally fixed manner.

As the second planetary wheel carrier P22 a is connected to the second hollow wheel P23 a in a rotationally fixed manner, the second planetary gear unit P2 a is blocked. The second planetary wheel carrier P22 a thus has a same speed as the drive unit 11 a. As the second planetary wheel carrier P22 a is connected to the third sun wheel P31 a in a rotationally fixed manner, the third sun wheel P31 a also has the same speed as the drive unit 11 a. The third hollow wheel P33 a is fixed, whereby the speed of the drive unit 11 a and the standing transmission ratio of the third planetary gear transmission P3 a is defined. The power output unit 12 a has the same speed as the third planetary wheel carrier P32 a. A power flow for the second forward transmission gear V2 a is introduced via the second planetary gear unit P2 a and is diverted via the third planetary gear unit P3 a.

The third forward transmission gear V3 a has a transmission ratio i₃a of 2.355 between the drive unit 11 a and the power output unit 12 a in this embodiment. The third forward transmission gear V3 a is formed by closing the clutch units S2 a, S3 a, S5 a. The clutch unit S2 a connects the first sun wheel P11 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S3 a connects the second planetary wheel carrier P22 a to the second hollow wheel P23 a and the first planetary wheel carrier P12 a in a rotationally fixed manner. The clutch unit S5 a connects the third hollow wheel P33 a to the transmission housing 13 a in a rotationally fixed manner.

The second sun wheel P21 a has a same speed as the drive unit 11 a. As the second planetary gear unit P2 a is blocked, the first planetary wheel carrier P12 a, which is connected to the second hollow wheel P23 a in a rotationally fixed manner, also has the same speed as the drive unit 11 a. As the first sun wheel P11 a is fixed, a speed of the first hollow wheel P13 a is defined by the speed of the drive unit 11 a and the standing transmission ratio of the first planetary gear unit P1 a. The third sun wheel P31 a is connected to the first hollow wheel P13 a in a rotationally fixed manner and thus has the same speed as the first hollow wheel P13 a. The third hollow wheel P33 a is fixed, whereby a speed of the third planetary wheel carrier P32 a, which is connected to the power output unit P11 a in a rotationally fixed manner, is defined by the standing transmission ratio of the third planetary gear unit P3 a and the speed of the third sun wheel P31 a. A power flow for the third forward transmission gear V3 a is introduced via the second planetary gear unit P2 a, guided further via the first planetary gear unit P1 a and is diverted again via the third planetary gear unit P3 a.

The fourth forward transmission gear V4 a has a transmission ratio i₄a of 1.698 between the drive unit 11 a and the power output unit 12 a in this embodiment. The fourth forward transmission gear V4 a is formed by closing the clutch units S2 a, S5 a, S6 a. The clutch unit S2 a connects the first sun wheel P11 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S5 a connects the third hollow wheel P33 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S6 a connects the fourth hollow wheel P43 a to the power output unit 12 a in a rotationally fixed manner.

The fourth planetary wheel carrier P42 a rotates with the same speed as the drive unit 11 a. The fourth sun wheel P41 a is connected to the third sun wheel P31 a in a rotationally fixed manner. The fourth hollow wheel P43 a is connected to the third planetary wheel carrier P32 a in a rotationally fixed manner. As the third hollow wheel P33 a is fixed, a speed ratio between the third sun wheel P31 a and the third planetary wheel carrier P32 a, which is the same as a speed ratio between the fourth sun wheel P41 a and the fourth hollow wheel P43 a, is defined by means of the standing transmission ratio of the third planetary gear unit P3 a. A speed of the power output unit 12 a, which is the same as the speed of the fourth hollow wheel P43 a, is thus defined by the standing transmission ratio of the fourth planetary gear unit P4 a, the speed ratio between the fourth sun wheel P41 a and the fourth hollow wheel P43 a and the speed of the drive unit 11 a. A power flow for the fourth forward transmission gear V4 a is introduced via the fourth planetary gear unit and split via the clutch unit S6 a. A part of the power flow is fed back to the fourth planetary gear unit P4 a via the third planetary gear unit P3 a. A further part of the power flow is diverted directly.

The fifth forward transmission gear V5 a has a transmission ratio i₅a of 1.236 between the drive unit 11 a and the power output unit 12 a in this embodiment. The fifth forward transmission gear V5 a is formed by closing the clutch units S2 a, S3 a, S6 a. The clutch unit S2 a connects the first sun wheel P11 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S3 a connects the second planetary wheel carrier P22 a to the second hollow wheel P23 a and the first planetary wheel carrier P12 a in a rotationally fixed manner. The clutch unit S6 a connects the fourth hollow wheel P43 a to the power output unit 12 a in a rotationally fixed manner.

The second sun wheel P21 a P21 a has a same speed as the drive unit 11 a. As the the second planetary wheel carrier P22 a is connected to the second hollow wheel P23 a in a rotationally fixed manner, the second planetary gear unit P2 a is blocked, whereby the second planetary wheel carrier P22 a and the second hollow wheel P23 a also have the same speed as the drive unit 11 a. The first sun wheel is fixed. The first planetary wheel carrier P12 a, which is connected to the second hollow wheel P23 a in a rotationally fixed manner, has the same speed as the drive unit 11 a. A speed of the first hollow wheel P13 a is thus defined by the standing transmission ratio of the first planetary gear unit P1 a and the speed of the drive unit 11 a. The fourth planetary wheel carrier P42 a also has the same speed as the drive unit 11 a. The fourth sun wheel P41 a has the same speed as the first hollow wheel P13 a. A speed of the fourth hollow wheel P43 a, which is connected to the power output unit 12 a in a rotationally fixed manner, is defined by means of the speed of the drive unit 11 a, the speed of the fourth sun wheel P41 a and the standing transmission ratio of the fourth planetary gear unit P4 a. A power flow for the fifth transmission gear V5 a is introduced via the fourth planetary gear unit P4 a and is split. A part of the power flow is fed back to the drive unit 11 a via the first planetary gear unit P1 a and the second planetary gear unit P2 a. A further part of the power flow is diverted again via the fourth planetary gear unit P4 a.

The sixth forward transmission gear V6 a has a transmission ratio i₆a of 1.000 between the drive unit 11 a and the power output 12 a in this embodiment. It is formed as a direct gear. The sixth forward transmission gear V6 a is formed by closing the clutch units S3 a, S4 a, S6 a. The clutch unit S3 a connects the second planetary wheel carrier P22 a to the second hollow wheel P23 a and the first planetary wheel carrier P12 a in a rotationally fixed manner. The clutch unit S4 a connects the second planetary wheel carrier P22 a to the fourth sun wheel P41 a in a rotationally fixed manner. The clutch unit S6 a connects the fourth hollow wheel P43 a to the power output 12 a in a rotationally fixed manner.

As the second planetary wheel carrier P22 a is connected to the second hollow wheel P23 a in a rotationally fixed manner, the second planetary gear unit P2 a is blocked. As the second sun wheel P21 a has a same speed as the drive unit 11 a, the second planetary wheel carrier P22 a and the fourth sun wheel P41 a also have the same speed as the drive unit 11 a. The fourth planetary wheel carrier P42 a, which is connected to the drive unit 11 a in a rotationally fixed manner, also has the same speed as the drive unit 11 a, whereby the fourth hollow wheel P43 a also has the same speed as the drive unit 11 a. A power flow for the sixth transmission gear V6 a is introduced via the fourth planetary gear unit P4 a and is split. A part of the power flow is fed back to the drive unit 11 a via the second planetary gear unit P2 a. A further part of the power flow is diverted again via the fourth planetary gear unit P4 a.

The seventh forward transmission gear V7 a has a transmission ratio i₇a of 0.881 between the drive unit 11 a and the power output 12 a in this embodiment. The seventh forward transmission gear V7 a is formed by closing the clutch units S2 a, S4 a, S6 a. The clutch unit S2 a connects the first sun wheel P11 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S4 a connects the second planetary wheel carrier P22 a to the fourth sun wheel P41 a in a rotationally fixed manner. The clutch unit S6 a connects the fourth hollow wheel P43 a to the power output 12 a in a rotationally fixed manner.

As the first sun wheel P11 a is fixed, a speed ratio between the first planetary wheel carrier P12 a and the first hollow wheel P13 a and thus also between the second hollow wheel P23 a and the second planetary wheel carrier P22 a by the standing transmission ratio of the first planetary gear unit P1 a. A speed of the fourth sun wheel P41 a, which is the same as a speed of the second hollow wheel P23 a, is thus defined by the speed ratio between the first planetary wheel carrier P12 a and the first hollow wheel P13 a and a speed of the drive unit 11 a. A speed of the fourth hollow wheel P43 a is defined by the speed of the fourth sun wheel P41 a, the speed of the drive unit 11 a and the standing transmission ratio of the fourth planetary gear unit P4 a. A power flow for the seventh forward transmission gear V7 a is introduced via the fourth planetary gear unit P4 a and is split. A part of the power flow is fed back to the drive unit 11 a via the second planetary gear unit P2 a and the first planetary gear unit P1 a. A further part of the power flow is diverted via the fourth planetary gear unit P4 a.

The eighth forward transmission gear V8 a has a transmission ratio i₈a of 0.726 between the drive unit 11 a and the power output 12 a in this embodiment. The eighth forward transmission gear V8 a is formed by closing the clutch units S1 a, S4 a, S6 a. The clutch unit S1 a connects the second planetary wheel carrier P22 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S4 a connects the fourth sun wheel P41 a to the second planetary wheel carrier P22 a and thus to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S6 a connects the fourth hollow wheel P43 a to the power output 12 a in a rotationally fixed manner.

The fourth sun wheel P41 a is fixed. The fourth planetary wheel carrier P42 a, which is connected to the drive unit 11 a in a rotationally fixed manner has a same speed as the drive unit 11 a. A speed of the fourth hollow wheel P43 a and thus a speed of the power output unit 12 a are defined by the speed of the drive unit 11 a and the standing transmission ratio of the fourth planetary gear unit P4 a. A power flow for the eighth forward transmission gear V8 is introduced and diverted via the fourth planetary gear unit P4 b.

The ninth forward transmission gear V9 a has a transmission ratio i₉a of 0.581 between the drive unit 11 a and the power output 12 a in this embodiment. The ninth forward transmission gear V9 b is formed by closing the clutch units S1 a, S2 a, S6 a. The clutch unit S1 a connects the second planetary wheel carrier P22 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S2 a connects the first sun wheel P11 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S6 a connects the fourth hollow wheel P43 a to the power output 12 a in a rotationally fixed manner.

The second planetary wheel carrier P22 a is fixed. The second sun wheel P21 a has a same speed as the drive unit 11 a. A speed of the second hollow wheel P23 a is defined by the speed of the drive unit 11 a and the standing transmission ratio of the second planetary gear unit P2 a. The first planetary wheel carrier P12 a has the same speed as the second hollow wheel P23 a. The first sun wheel P11 a is fixed. A speed of the first hollow wheel P13 a is defined by the speed of the second hollow wheel P23 a and the standing transmission ratio of the first planetary gear unit P1 a. The speed of the fourth sun wheel P41 a is the same as the speed of the first hollow wheel P13 a. The fourth hollow wheel P42 a has a same speed as the drive unit 11 a. A speed of the fourth hollow wheel P43 a, which is connected to the power output 12 a in a rotationally fixed manner, is defined by the speed of the second hollow wheel P23 a, the standing transmission ratio of the fourth planetary gear unit P4 a and the speed of the drive unit 11 a. A power flow for the ninth forward transmission gear V9 a introduced via drive unit 11 a is split before the first planetary gear unit P1 a. A first part of the power flow is guided to the fourth planetary gear unit P4 a via the second planetary gear unit P2 a and the first planetary gear unit P1 a. A second part of the power flow is guided directly to the fourth planetary gear unit P4 a. The power flow is combined again and diverted by means of the fourth planetary gear unit P4 a.

The reverse transmission gear R1 a has a transmission ratio i_(R)a of −3.905 between the drive unit 11 b and the power output unit 12 a in this embodiment. The reverse transmission gear R1 a is formed by closing the clutch units S1 a, S2 a, S5 a. The clutch unit S1 a connects the second planetary wheel carrier P22 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S2 a connects the first sun wheel P11 a to the transmission housing 13 a in a rotationally fixed manner. The clutch unit S5 a connects the third hollow wheel P33 a to the transmission housing 13 a in a rotationally fixed manner.

The second planetary wheel carrier P22 a is fixed. The second sun wheel P21 a has a same speed as the drive unit 11 a. A speed of the second hollow wheel P23 a is defined by the speed of the drive unit 11 a and the standing transmission ratio of the second planetary gear unit P2 a. The first planetary wheel carrier P12 a has the same speed as the second hollow wheel P23 a. The first sun wheel P11 a is fixed. A speed of the first hollow wheel P13 a is defined by the speed of the second hollow wheel P23 a and the standing transmission ratio of the first planetary gear unit P1 a. The speed of the third sun wheel P31 a is the same as the speed of the first hollow wheel P13 a. The third hollow wheel P33 a is fixed. A speed of the third planetary wheel carrier P32 a, which is connected to the power output 12 a in a rotationally fixed manner, is defined by the speed of the first hollow wheel P13 a and the standing transmission ratio of the third planetary gear unit P3 a. A power flow for the reverse transmission gear R1 a is introduced via the second planetary gear transmission P2 a, guided to the third planetary gear unit P3 a via the first planetary gear unit P1 a, and is diverted again via the third planetary gear unit P3 a.

A progressive ratio φ_(1/2)a between the first and the second forward transmission gear V1 a, V2 a is 1.557. A progressive ratio φ_(2/3)a between the second and the third forward transmission gear V2 a, V3 a is 1.506. A progressive ratio φ_(3/4)a between the third and the fourth forward transmission gear V3 a, V4 a is 1 .387. A progressive ratio φ_(4/5)a between the fourth and the fifth forward transmission gear V4 a, V5 a is 1.374. A progressive ratio φ_(5/6)a between the fifth and the sixth forward transmission gear V5 a, V6 a is 1.236. A progressive ratio φ_(6/7)a between the sixth and the seventh forward transmission gear V6 a, V7 a is 1.135. A progressive ratio φ_(7/8)a between the seventh and the eighth forward transmission gear V7 a, V8 a is 1.214. A progressive ratio φ_(8/9)a between the eighth and the ninth forward transmission gear V8 a, V9 a is 1.249. A total spread of the transmission unit between the first forward transmission gear V1 a and the ninth forward transmission gear V9 a is about 9.5. A spread between the first forward transmission gear V1 a and the eighth forward transmission gear V8 a is about 7.6. A spread between the second forward transmission gear V2 a and the ninth forward transmission gear V9 a is about 6.1 (see FIG. 2). The transmission unit can basically also be used as an eight gear transmission.

A maximum speed factor for the planetary gear unit P1 a, P2 a, P3 a, P4 a is about 2.7. A maximum speed factor for the planetary gear units P1 a, P2 a, P3 a, P4 a is about 3.3 in the forward transmission gear V9 a. The speed factor for the planetary gear units P1 a, P2 a, P3 a, P4 a describes a ratio between a speed of the drive unit 11 a and a maximum speed, which occurs at the sun wheels P11 a, P21 a, P31 a, P41 a, the hollow wheels P13 a, P23 a, P33 a, P43 a or the planetary wheel carriers P12 a, P22 a, P32 a, P42 a in one of the forward transmission gears V1 a-V9 a. A maximum speed factor for the planetary wheels P14 a, P24 a, P34 a, P44 a is about 3.0 in the forward transmission gears V1 a-V8 a and about 3.3 in the ninth forward transmission gear V9 a. A maximum speed of the drive unit 11 a and thus a speed of the planetary wheels P14 a, P24 a, P34 a, P44 a can be limited in the ninth forward transmission gear V9 a.

A maximum torque factor is about 5.5 for the forward transmission gears V1 a-V9 a. The torque factor describes a ratio between between a drive torque applied at a drive unit 11 a and a maximum torque occurring at the sun wheels P11 a, P21 a, P31 a, P41 a, the hollow wheels P13 a, P23 a, P33 a, P43 a or the planetary wheel carriers P12 a, P22 a, P32 a, P42 a. The maximum torque factor for the forward transmission gears V1 a-V9 a is achieved in the first forward transmission gear V1 a.

A shiftability of the forward transmission gears V1 a-V9 a is shown in FIG. 4. The forward transmission gears V2 a, V3 a, V4 a, V7 a can be shifted starting with the first forward transmission gear V1 a. The forward transmission gears V1 a, V3 a, V6 a can be shifted starting with the second forward transmission gear V2 a. The forward transmission gears V1 a, V2 a, V4 a, V5 a can be shifted starting with the third forward transmission gear V3 a. The forward transmission gears V4 a, V5 a, V7 a, V9 a can be shifted starting with the fourth forward transmission gear V4 a. The forward transmission gears V3 a, V4 a, V6 a, V7 a, V9 a can be shifted starting with the fifth forward transmission gear V5 a. The forward transmission gears V 2 a, V5 a, V7 a, V8 a can be shifted starting with the sixth forward transmission gear V6 a. The forward transmission gears V1 a, V4 a, V5 a, V6 a, V8 a, V9 a can be shifted starting with the seventh forward transmission gear V7 a. The forward transmission gears V6 a, V7 a, V9 a can be shifted starting with the eighth forward transmission gear V8 a. The forward transmission gears V4 a, V5 a, V7 a, V8 a can be shifted starting with the ninth forward transmission gear V9 a.

In FIGS. 5 to 6 is shown a further embodiment of the invention. For distinguishing the embodiments, the letter “a” is replaced in the reference numerals of the embodiment in FIGS. 1 and 4 by the letter b in the reference numerals of the embodiments in FIGS. 5 to 6. The following description is essentially restricted to differences between the embodiments. With regard to the same components, characteristics and functions, one can refer to the description and/or the drawings of the embodiment in FIGS. 1 to 4.

FIG. 5 shows a transmission designed as a motor vehicle transmission. The transmission has four planetary gear units P1 b, P2 b, P3 b, P4 b. The first planetary gear unit P1 b, the second planetary gear unit P2 b, the third planetary gear unit P3 b and the fourth planetary gear unit P4 b are arranged behind each other along a main axis of rotation 10 b. The transmission has six clutch units S1 b, S2 b, S3 b, S4 b, S5 b, S6 b. These are provided to shift exactly nine forward transmission gears V1 b, V2 b, V3 b, V4 b, V5 b, V6 b, V7 b, V8 b, V9 b. The transmission can however also be operated with only eight forward transmission gears, for example in that the first forward transmission gear V1 b or the ninth forward transmission gear V9 b is not shifted.

The first planetary gear unit P1 b is arranged on the input side. The first planetary gear unit P1 b has a single planetary wheel set. The single planetary wheel set comprises a first sun wheel P11 b, a first hollow wheel P13 b and a first planetary wheel carrier P12 b. The first planetary gear unit P1 b has a standing transmission ratio of −1.970 between the sun wheel P11 b and the hollow wheel P13 b with a fixed planetary wheel carrier P12 b.

The second planetary gear unit P2 b is arranged centrally on the input side. The second planetary gear unit P2 b has a single planetary wheel set. The single planetary wheel set comprises a second sun wheel P21 b, a second hollow wheel P23 b and a second planetary wheel carrier P22 b. The second planetary gear unit P2 b has a standing transmission ratio of −1.654 between the sun wheel P21 b and the hollow wheel P23 b with a fixed planetary wheel carrier P22 b.

The third planetary gear unit P3 b is arranged centrally on the output side. The third planetary gear unit P3 b has a single planetary wheel set. The single planetary wheel set comprises a third sun wheel P31 b, a third hollow wheel P33 b and a third planetary wheel carrier P32 b. The third planetary gear unit P3 b has a standing transmission ratio of −2.556 between the sun wheel P31 b and the hollow wheel P33 b with a fixed planetary wheel carrier P32 b.

The fourth planetary unit P4 b is arranged on the output side. The fourth planetary gear unit P4 b has a single planetary wheel set. The single planetary wheel set comprises a fourth sun wheel P41 b, a fourth hollow wheel P43 b and a fourth planetary wheel carrier P42 b. The fourth planetary gear unit P4 b as a standing transmission ratio of −2.644 between the sun wheel P41 b and the hollow wheel P43 b with a fixed planetary wheel carrier P42 b.

The three clutch units S3 b, S4 b, S6 b formed as clutch units respectively have one first rotatable clutch element S31 b, S41 b, S61 b and a second rotatable clutch element S32 b, S42 b, S62 b which can be connected to each other in a rotationally fixed manner by means of the corresponding clutch units S3 b, S4 b, S6 b. The three clutch units S1 b, S2 b, S5 b formed as brake units respectively only have one clutch element S11 b, S21 b, S51 b, which can be connected to a transmission housing 13 b in a rotationally fixed manner by means of the corresponding clutch units S1 b, S2 b, S5 b.

The clutch units S1 b, S2 b, S3 b, S5 b are arranged on the outside. The clutch units S4 b, S6 b are designed as lying on the inside. The clutch units S1 b, S2 b, S3 b, S6 b are in the form of disc packets. The clutch unit S5 b is in the form of a dog clutch unit. It has a synchronising unit, not shown in detail, which can basically also be omitted. The clutch unit S5 b can however also in the form of a disc packet. The clutch units S3 b, S1 b, S2 b are arranged in the axial direction at the input side from the first planetary gear unit P1 b in this sequence. The clutch unit S4 b is arranged in the axial direction between the second planetary gear unit P2 b and the third planetary gear unit P3 b. The clutch unit S5 b is arranged in the axial direction at the level of the fourth planetary gear unit P3 b. The clutch unit S6 b is arranged in the axial direction at the level of the fourth planetary gear unit P4 b.

The drive unit 11 b is connected to the second sun wheel P21 b, the fourth planetary wheel carrier P42 b and the first clutch element S31 b of the third clutch unit S3 b in a rotationally fixed manner by means of a drive shaft 14 b which is connected to the drive unit 11 b. The first sun wheel P11 b and the clutch element S21 b of the second clutch unit S2 b are connected in a rotationally fixed manner by means of a connection shaft 16 b. The first hollow wheel P13 b, the clutch element S42 b of the fourth clutch unit S4 b, the third sun wheel 31 b and the fourth sun wheel P41 b are connected in a rotationally fixed manner by means of a connection shaft 17 b. The clutch element S32 b of the third clutch unit S3 b, the clutch element S11 b of the first clutch unit S1 b, the second planetary wheel carrier P22 b and the clutch element S41 b of the fourth clutch unit S4 b are connected in a rotationally fixed manner by means of a connection shaft 18 b. The first planetary wheel carrier P12 b and the second hollow wheel P23 b are connected in a rotationally fixed manner by means of a connection shaft 19 b. The third hollow wheel P33 b is directly connected to the clutch element S51 b of the fifth clutch unit S5 b in a rotationally fixed manner. The fourth hollow wheel P43 b is directly connected to the clutch element S61 b of the sixth clutch unit S6 b in a rotationally fixed manner. The power output unit 12 b is connected in a rotationally fixed manner to the third planetary wheel carrier P32 b and the clutch element S62 b of the sixth clutch unit S6 b by means of a power output shaft 15 b.

The drive shaft 14 b, which is connected to the drive unit 11 b, passes through the four sun wheels P11 b, P21 b, P31 b, P41 b. For the connection of the clutch element S31 b, it is guided axially to the outside at the input side. The drive shaft 14 b limits the transmission on the input side The second hollow wheel P23 b is connected directly to the drive shaft 14 b. For connecting the fourth planetary wheel carrier P42 b, the drive shaft 14 b is guided axially and radially between the fourth planetary gear unit P4 b and the power output shaft 15 b. The connection shaft 16 b is guided radially to the outside on the axial input side from the first planetary gear unit P1 b. The connection shaft 17 b surrounds the second planetary gear unit P2 b. It is guided radially and axially to the inside between the clutch unit S4 b and the third planetary gear unit P3 b and connected to the third sun wheel P31 b and the fourth sun wheel P41 b. The connection shaft 18 a is guided radially and axially to the outside between the drive shaft 14 b and the connection shaft 16 b. It further passes through the first sun wheel P11 b and is guided to the outside radially and axially between the planetary gear units P1 b, P2 b for connecting the second planetary wheel carrier P22 b. For the connection of the clutch element S42 b, it passes through the second planetary gear unit P2 b and is guided radially and axially to the outside between the second planetary gear unit P2 b and the connection shafts 17 b. The connection shaft 19 b is guided radially and axially to the outside between the first planetary gear unit P1 b and the second planetary gear unit P2 b for connecting the planetary wheel carrier P12 b and the hollow wheel P23 b. The power output shaft 15 b is guided axially and radially to the outside between the third planetary gear unit P3 b and the fourth planetary gear unit P4 b. It surrounds the fourth planetary gear unit P4 b and limits the transmission unit on the output side.

The forward transmission gears V1 b-V9 b are shifted by means of the clutch units S1 b, S2 b, S3 b, S4 b, S5 b, S6 b (see FIG. 6). The transmissions of the two embodiments are kinematically equivalent. The clutch unit S3 b has a changed clutch compared to the previous embodiment, this is why the transmission gears V1 b-V9 b have changed power flows particularly with regard to a strain on the connection shafts 16 b, 17 b, 18 b, 19 b. A shift logic of the transmission unit is unchanged. Due to the changed standing transmission ratio of the planetary gear units P2 b, P3 b, P4 b, the transmission gears V1 b-V9 b have different transmission ratios 1 ₁b-1 ₉b. For shifting the forward transmission gears V2 b, V3 b, V5 b, V6 b, the second sun wheel P21 b and the second planetary wheel carrier P22 a can be connected in a rotationally fixed manner by means of the clutch unit S3 b, whereby the second planetary gear unit P2 b can be blocked by means of the clutch unit S3 b.

The first forward transmission gear V1 b has a transmission ratio i₁ b of 5.5536 between the drive unit 11 b and the power output unit 12 b in this embodiment. The first forward transmission gear V1 b is formed by closing the clutch units S2 b, S4 b, S5 b. The clutch unit S2 b connects the first sun wheel P11 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S4 b connects the second planetary wheel carrier P22 b to the first hollow wheel P13 b and the third sun wheel P31 b in a rotationally fixed manner. The clutch unit S5 b connects the third hollow wheel P33 b to the transmission housing 13 b in a rotationally fixed manner. A power flow for the first unit gear V1 b is introduced via the second planetary gear unit P2 b and is split via the clutch unit S4 b. A part of the power flow is fed back to the second planetary gear unit P2 b via the first planetary gear unit P1 b. A further part of the power flow is diverted via the third planetary gear unit P3 b.

The second forward transmission gear V2 b has a transmission ratio i₂b of 3.556 between the drive unit 11 b and the power output unit 12 b in this embodiment. The second forward transmission gear V2 b is formed by closing the clutch units S3 b, S4 b, S5 b. The clutch unit S3 b connects the second planetary wheel carrier P22 b to the second sun wheel P21 b in a rotationally fixed manner. The clutch unit S4 b connects the second planetary wheel carrier P22 b to the third sun wheel P31 b in a rotationally fixed manner. The clutch unit S6 b connects the third hollow wheel P33 b to the transmission housing 13 b in a rotationally fixed manner. A power flow for the second forward transmission gear V2 b is introduced via the second planetary gear unit P2 b and is diverted via the third planetary gear unit P3 b.

The third forward transmission gear V3 b has a transmission ratio i₃b of 2.359 between the drive unit 11 b and the power output unit 12 b in this embodiment. The third forward transmission gear V3 b is formed by closing the clutch units S2 b, S3 b, S5 b. The clutch unit S2 b connects the first sun wheel P11 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S3 b connects the second planetary wheel carrier P22 b to the second sun wheel P21 b in a rotationally fixed manner. The clutch unit S5 b connects the third hollow wheel P33 b to the transmission housing 13 b in a rotationally fixed manner. A power flow for the third forward transmission gear V3 b is introduced via the second planetary gear unit P2 b, guided further via the first planetary gear unit P1 b and is again diverted via the third planetary gear unit P3 b.

The fourth forward transmission gear V4 b has a transmission ratio i₄b of 1.701 between the drive unit 11 b and the power output unit 12 b in this embodiment. The fourth forward transmission gear V4 b is formed by closing the clutch units S2 b, S5 b, S6 b. The clutch unit S2 b connects the first sun wheel P11 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S5 b connects the third hollow wheel P33 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S6 b connects the fourth hollow wheel P43 b to the power output unit 12 b in a rotationally fixed manner. A power flow for the fourth forward transmission gear V4 b is introduced via the fourth planetary gear unit P4 b and is split via the clutch unit S6 b. A part of the power flow is fed back to the fourth planetary gear unit P4 b via the third planetary gear unit P3 b. A further part of the power flow is diverted directly.

The fifth forward transmission gear V5 b has a transmission ratio i₅b of 1.238 between the drive unit 11 b and the power output unit 12 b in this embodiment. The fifth forward transmission gear V5 b is formed by closing the clutch units S2 b, S3 b, S6 b. The clutch unit S2 b connects the first sun wheel P11 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S3 b connects the second planetary wheel carrier P22 b to the second sun wheel P21 b in a rotationally fixed manner. The clutch unit S6 b connects the fourth hollow wheel P43 b to the power output unit 12 b in a rotationally fixed manner. A power flow for the fifth forward transmission gear V6 b is split by means of the drive shaft 11 b. A part of the power flow is diverted directly via the fourth planetary gear unit P4 b, a further part is fed back to the drive unit 11 b via the blocked second planetary gear unit P2 b. A part of the power flow guided via the fourth planetary gear unit P4 b is also guided to the second planetary gear unit P2 b via the first planetary gear unit P1 b.

The sixth forward transmission gear V6 b has a transmission ratio i_(s)b of 1.000 between the drive unit 11 b and the power output unit 12 b in this embodiment. It is formed as a direct gear. The sixth forward transmission gear V6 b is formed by closing the clutch units S3 b, S4 b, S6 b. The clutch unit S3 b connects the second planetary wheel carrier P22 b to the fourth sun wheel P41 b in a rotationally fixed manner. The clutch unit S4 b connects the second planetary wheel carrier P22 b to the fourth sun wheel P41 b in a rotationally fixed manner. The clutch unit S6 b connects the fourth hollow wheel P43 b to the power output unit 12 b in a rotationally fixed manner. A power flow for the sixth forward transmission gear V6 b is introduced via the fourth planetary gear unit P4 b and is split. A part of the power flow is fed back to the drive unit 11 b via the second planetary gear unit P2 b. A further part of the power flow is diverted again via the fourth planetary gear unit P4 b.

The seventh forward transmission gear V7 b has a transmission ratio i₇b of 0.881 between the drive unit 11 b and the power output unit 12 b in this embodiment. The seventh forward transmission gear V7 b is formed by closing the clutch units S2 b, S4 b, S6 b. The clutch unit S2 b connects the first sun wheel P11 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S4 b connects the second planetary wheel carrier P22 b to the fourth sun wheel P41 b in a rotationally fixed manner. The clutch unit S6 b connects the fourth hollow wheel P43 b to the power output unit 12 b in a rotationally fixed manner. A power flow for the seventh forward transmission gear V7 b is introduced via the fourth planetary gear unit P4 b and is split. A part of the power flow is fed back to the drive unit 11 b via the second planetary gear unit P2 b and the first planetary gear unit P1 b. A further part of the power flow is diverted via the fourth planetary gear unit P4 b.

The eighth forward transmission gear V8 b has a transmission ratio i₈b of 0.726 between the drive unit 11 b and the power output unit 12 b in this embodiment. The eighth forward transmission gear V8 b is formed by closing the clutch units S1 b, S4 b, S6 b. The clutch unit S1 b connects the second planetary wheel carrier P22 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S4 b connects the fourth sun wheel P41 b to the second planetary wheel carrier P22 b and thus to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S6 b connects the fourth hollow wheel P43 b to the drive unit in a rotationally fixed manner. A power flow for the eighth forward transmission gear V8 b is introduced and diverted via the fourth planetary gear unit P4 b.

The ninth forward transmission gear V9 b has a transmission ratio i₉b of 0.580 between the drive unit 11 b and the power output unit 12 b in this embodiment. The ninth forward transmission gear V9 b is formed by closing the clutch units S1 b, S2 b, S5 b. The clutch unit S1 b connects the second planetary wheel carrier P22 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S2 b connects the fourth hollow wheel P43 b to the drive unit 12 b in a rotationally fixed manner. A power flow for the ninth forward transmission gear V9 b introduced via the drive unit 11 b is split in front of the first planetary gear unit P1 b. A first part of the power flow is guided to the fourth planetary gear unit P4 b via the second planetary gear unit P2 b and the first planetary gear unit P1 b. A second part of the power flow is directly guided to the fourth planetary gear unit P4 b. The power flow is combined again and diverted by means of the fourth planetary gear unit P4 b.

The reverse transmission gear R1 b has a transmission ratio i_(R)b of −3.901 between the drive unit 11 b and the power output unit in this embodiment. The reverse transmission gear R1 b is formed by closing the clutch units S1 b, S2 b, S5 b. The clutch unit S1 b connects the second planetary wheel carrier P22 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S2 b connects the first sun wheel P11 b to the transmission housing 13 b in a rotationally fixed manner. The clutch unit S5 b connects the third hollow wheel P33 b to the transmission housing 13 b in a rotationally fixed manner. A power flow for the reverse transmission gear R1 b is introduced via the second planetary gear unit P2 b, guided to the third planetary gear unit P3 b via the first planetary gear unit P1 b and is diverted again via the third planetary gear unit P3.

A progressive ratio φ_(1/2)b between the first and the second forward transmission gear V1 b V1 b, V2 b is 1.557. A progressive ratio φ_(2/3)b between the second and the third forward transmission gear V2 b, V3 b is 1.508. A progressive ratio φ_(3/4)b between the third and the fourth forward transmission gear V3 b, V4 b is 1.386. A progressive ratio φ_(4/5)b between the fourth and the fifth forward transmission gear V4 b, V5 b is 1.375. A progressive ratio φ_(5/6)b between the fifth and the sixth forward transmission gear V5 b, V6 b is 1.238. A progressive ratio φ_(6/7)b between the sixth and the seventh forward transmission gear V6 b, V7 b is 1.135. A progressive ratio φ_(7/8)b between the seventh and the eighth forward transmission gear V7 b, V8 b is 1.214. A progressive φ_(8/9)b ratio between the eighth and the ninth forward transmission gear V8 b, V9 b is 1.250. A total spread of the transmission unit between the first forward transmission gear V1 b and the ninth forward transmission gear V9 b is about 9.5. A spread between the first forward transmission gear V1 b and the eighth forward transmission gear V8 b is about 7.6. A spread between the second forward transmission gear V2 b and the ninth forward transmission gear V9 b is about 6.1. The transmission unit can basically also be used as an eight gear transmission. 

What is claimed is:
 1. A transmission unit, having in a transmission housing (13 a, 13 b), a first, a second, a third, and a fourth planetary gear unit (P1 a, P2 a, P3 a, P4 a; P1 b, P2 b, P3 b, P4 b) disposed along a main axis of rotation (10 a; 10 b) and including first, second, third and fourth respective sun gears (P11 a, P21 a, P31 a, P41 a, P11 b, P21 b, P31 b, P41 b) and respective first, second, third and fourth planetary gear carriers(P12 a, P22 a, P32 a, P42 a, P12 b, P22 b, P32 b, P42 b), with the first planetary wheel carrier (P12 a ; P12 b) and a second hollow wheel (P23 a ; P23 b ), being connected to each other in a rotationally fixed manner and with six clutch units (S1 a, S2 a, S3 a, S4 a, S5 a, S6 a; S1 b, S2 b, S3 b, S4 b, S5 b, S6 b) allowing for nine forward gears (V1 a-V9 a; V1 b-V9 b) to be engaged, with a drive unit (11 a; 11 b) rotationally fixedly connected to the second sun gear (P21 a; P21 b) of the second planetary gear units (P2 a; P2 b) and the fourth planetary wheel carrier (P42 a; P42 b) of the fourth planetary gear unit (P4 a; P4 b), and having a power output unit (12 a; 12 b) rotationally fixedly connected to the third planetary wheel carrier (P32 a; P32 b) of the third planetary gear transmission (P3 a; P3 b).
 2. The transmission unit according to claim 1, wherein a clutch element (S61 a; S61 b) of the hollow gear (43 a )of the fourth planetary gear unit (P4 a, P4 b) is connected to the power output unit (12 a; 12 b) in a rotationally fixed manner.
 3. The transmission unit according to claim 2, wherein the planetary gear units include respective first, second, third and fourth hollow wheels and the fourth hollow wheel (P43 a; P43 b) and a clutch element (S62 a; S62 b) are connected to each other in a rotationally fixed manner.
 4. The transmission unit according to claim 2, wherein one of the clutch units (S6 a; S6 b) is provided to connect, in a rotationally fixed manner, the clutch element (S61 a; S61 b) which is connected to the power output unit (12 a; 12 b) in a rotationally fixed manner and the clutch element (S62 a; S62 b) which is connected to the fourth hollow wheel (P43 a; P43 b) in a rotationally fixed manner.
 5. The transmission unit according to claim 3, wherein the third hollow wheel (P33 a; P33 b) and a clutch element (S51 a; S51 b) are connected to each other in a rotationally fixed manner.
 6. The transmission unit according to claim 5, wherein one of the clutch units (S5 a; S5 b) is provided to connect, in a rotationally fixed manner, the clutch element (S51 a; S51 b) connected to the third hollow wheel (P33 a; P33 b) in a rotationally fixed manner to the transmission housing (13 a; 13 b).
 7. The transmission unit according to claim 1, wherein a first hollow wheel (P13 a; P13 b), a clutch element (S42 a; S42 b), a third sun wheel (P31 a; P31 b) and a fourth sun wheel (P41 a; P41 b), are all interconnected in a rotationally fixed manner.
 8. The transmission unit according to claim 1, wherein three clutch elements (S11 a, S32 a, S41 a; S11 b, S32 b, S43 b) and a second planetary wheel carrier (P22 a; P22 b), are all interconnected to each other in a rotationally fixed manner.
 9. The transmission unit according to claims 7, wherein one of the clutch units (S4 a; S4 b) is provided to connect in a rotationally fixed manner one of the clutch elements (S41 a; S41 b) connected to the second planetary wheel carrier (P22 a; P22 b) in a rotationally fixed manner and the clutch element (S42 a; S42 b) connected to the first hollow wheel (P13 a; P13 b) in a rotationally fixed manner.
 10. The transmission unit at least according to claim 8, wherein one of the of the clutch units (S1 a; S1 b) is provided to connect in a rotationally fixed manner one of the clutch elements (S11 a; S11 b) connected to the second planetary wheel carrier (P22 a; P22 b) in a rotationally fixed manner to the transmission housing (13 a).
 11. The transmission unit according to claim 1, wherein a first sun wheel (P11 a; P11 b) and a clutch element (S21 a; S21 b) are connected to each other in a rotationally fixed manner.
 12. The transmission unit according to claim 11, wherein one of the clutch units (S2 a; S2 b) is provided to connect in a rotationally fixed manner the clutch element (S21 a; S21 b) connected to the first sun wheel (P11 a; P11 b) in a rotationally fixed manner to the transmission housing (13 a; 13 b).
 13. The transmission unit according to claim 1, wherein a clutch element (S31 a; S31 b) is connected to one of the second hollow wheel (P23 a) and the second sun wheel (P21 b) in a rotationally fixed manner.
 14. The transmission unit according to claim 13, wherein one of the clutch units (S3 a, S3 b) is provided to connect in a rotationally fixed manner one of the clutch elements (S32 a, S32 b) connected in a rotationally fixed manner to the second planetary wheel carrier (P22 a; P22 b) and the clutch element (S31 a; S31 b) connected in a rotationally fixed manner to the hollow wheel (P23 a) or the second sun wheel (P21 b). 